2026 ICD-10-CM Diagnosis Code D81.1Severe combined immunodeficiency [SCID] with low T- and B-cell numbers

ICD-10-CM Codes›D50–D89›D80-D89›D81

ICD-10-CM D81.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

D81.1 is a billable ICD-10-CM diagnosis code for severe combined immunodeficiency [SCID] with low T- and B-cell numbers. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 808 through 810. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Immunity disorders.

Code Identity

ICD-10-CM Code
D81.1
Billable Status
Yes — Valid for Submission
Code Describes
Severe combined immunodeficiency [SCID] with low T- and B-cell numbers
Short Description
Severe combined immunodeficiency w low T- and B-cell numbers
Parent Code
D81
Combined immunodeficiencies

Code Classification

ChapterD50–D89Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism
SectionD80-D89Certain disorders involving the immune mechanism
CategoryD81Combined immunodeficiencies
This CodeD81.1Severe combined immunodeficiency [SCID] with low T- and B-cell numbers

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Autosomal dominant T-cell negative, B-cell negative severe combined immunodeficiency due to activated RAC2 defect
  • Combined immunodeficiency due to partial RAG1 deficiency
  • Disorder of eosinophil
  • Hereditary eosinophilia
  • Omenn syndrome
  • SCID due to absent peripheral T cell maturation
  • SCID due to absent T cell receptor
  • SCID production
  • SCID due to absent IL-2 receptor
  • Severe combined immunodeficiency due to complete RAG1 and/or RAG2 deficiency
  • Severe combined immunodeficiency due to CTPS1 deficiency
  • Severe combined immunodeficiency due to LCK deficiency
  • Severe combined immunodeficiency with low T- and B-cell numbers

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Immunodeficiency
      • combined
        • severe (SCID)
          • with
            • low T- and B-cell numbers

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR BLD008
Immunity disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Omenn Syndrome

    a genetically heterogenous autosomal recessive severe combined immunodeficiency syndrome. caused by mutation(s) in the rag-1, rag-2, and dclre1c genes. it is characterized by the presence of alopecia, erythroderma, desquamation, lymphadenopathy, and chronic diarrhea.

  • Severe Combined Immunodeficiency due to RAG Deficiency with Omenn Syndrome|SCID, T-B-NK+ (RAG mutation) without Omenn Syndrome

    t-cell negative (t-), b-cell negative (b-) severe combined immunodeficiency (scid) caused by missense mutation(s) in the rag1 and/or rag2 genes, from which proteins encoded for by these gene(s) retain partial biologic activity that result in a less severe form of classical t-b-scid, along with clinical features of omenn syndrome.

  • Severe Combined Immunodeficiency due to RAG Deficiency without Omenn Syndrome|SCID, T-B-NK+ (RAG mutation) without Omenn Syndrome

    a rare severe combined immunodeficiency disorder caused by null mutations in recombination activating gene rag1 or rag2. phenotypically, it is toward the more severe end of the clinical spectrum due to complete arrest of t and b-cell development, without the clinical features of omenn syndrome.

Patient EducationClinical

Immune System and Disorders

Your immune system is a complex network of cells, tissues, and organs. Together they help the body fight infections and other diseases.

The full article covers:

  • What is the immune system?
  • What are the parts of the immune system?
  • How does the immune system work?
  • What are the types of immunity?
  • What can go wrong with the immune system?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert D81.1 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
279.2 Combined immunity defic
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About D81.1Overview

Is D81.1 (Combined immunodeficiencies) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report severe combined immunodeficiency [SCID] with low T- and B-cell numbers on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does D81.1 group to?

When severe combined immunodeficiency [SCID] with low T- and B-cell numbers is the principal diagnosis on an inpatient stay, it groups to MS-DRG 808, 809, 810, with relative weights from 1.0466 to 2.2079 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of D81.1?

Under the General Equivalence Mappings, severe combined immunodeficiency [SCID] with low T- and B-cell numbers converts to ICD-9-CM 279.2 (combined immunity defic). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.